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Park SH, Heo Y, Kwon I, Jo S, Jeon H, Lee Y, Kim J, Heo JH, Namkung W. Gestodene, a novel positive allosteric modulator of PAR1, enhances PAR1-mediated human platelet aggregation. Front Pharmacol 2024; 15:1430548. [PMID: 39130626 PMCID: PMC11310598 DOI: 10.3389/fphar.2024.1430548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2024] [Accepted: 07/12/2024] [Indexed: 08/13/2024] Open
Abstract
Background: Protease-activated receptor 1 (PAR1) is expressed in human platelets and can be activated by low concentrations of thrombin. Vorapaxar, a selective antagonist of PAR1, inhibits thrombin-induced calcium mobilization in human platelet, which is associated with an increased risk of bleeding. Conversely, the administration of a positive allosteric modulator (PAM) of PAR1 may pose a substantial risk of thrombosis due to inducing excessive platelet activation. In this study, we discovered a novel PAM of PAR1 and investigated the effect of enhanced PAR1 activation by PAM of PAR1 on platelet activation. Methods: To find PAMs of PAR1, a cell-based screen was performed in HT29 cells, and finally, gestodene, an oral contraceptive drug (OC), was identified as a novel PAM of PAR1. The mechanism of action of gestodene and its effects on platelet activation were investigated in human megakaryocytic leukemia cell line MEG-01 cells and human platelet. Results: Gestodene enhanced both thrombin- and PAR1-activating peptide (AP)-induced intracellular calcium levels in a dose-dependent manner without altering PAR2 and PAR4 activity. Gestodene significantly increased PAR1-AP-induced internalization of PAR1 and phosphorylation of ERK1/2, and the enhancing effects were significantly blocked by vorapaxar. Furthermore, gestodene potently increased PAR1-AP induced morphological changes in MEG-01 cells. Remarkably, in human blood, gestodene exerted a robust augmentation of PAR1-AP-induced platelet aggregation, and vorapaxar effectively attenuated the gestodene-induced enhancement of platelet aggregation mediated by PAR1. Conclusion: Gestodene is a selective PAM of PAR1 and suggest one possible mechanism for the increased risk of venous thromboembolism associated with OCs containing gestodene.
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Affiliation(s)
- So-Hyeon Park
- College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, Republic of Korea
| | - Yunkyung Heo
- College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, Republic of Korea
| | - Il Kwon
- Integrative Research Institute for Cerebrovascular and Cardiovascular Diseases, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Sungwoo Jo
- College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, Republic of Korea
| | - Hyejin Jeon
- College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, Republic of Korea
| | - Yechan Lee
- College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, Republic of Korea
| | - Jieun Kim
- Graduate Program of Industrial Pharmaceutical Science, Yonsei University, Incheon, Republic of Korea
| | - Ji Hoe Heo
- Department of Neurology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Wan Namkung
- College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, Republic of Korea
- Graduate Program of Industrial Pharmaceutical Science, Yonsei University, Incheon, Republic of Korea
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2
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Giannella A, Ceolotto G, Radu CM, Cattelan A, Iori E, Benetti A, Fabris F, Simioni P, Avogaro A, Vigili de Kreutzenberg S. PAR-4/Ca 2+-calpain pathway activation stimulates platelet-derived microparticles in hyperglycemic type 2 diabetes. Cardiovasc Diabetol 2021; 20:77. [PMID: 33812377 PMCID: PMC8019350 DOI: 10.1186/s12933-021-01267-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/22/2021] [Indexed: 02/07/2023] Open
Abstract
Background Patients with type 2 diabetes (T2DM) have a prothrombotic state that needs to be fully clarified; microparticles (MPs) have emerged as mediators and markers of this condition. Thus, we investigate, in vivo, in T2DM either with good (HbA1c ≤ 7.0%; GGC) or poor (HbA1c > 7.0%; PGC) glycemic control, the circulating levels of MPs, and in vitro, the molecular pathways involved in the release of MPs from platelets (PMP) and tested their pro-inflammatory effects on THP-1 transformed macrophages. Methods In 59 T2DM, and 23 control subjects with normal glucose tolerance (NGT), circulating levels of CD62E+, CD62P+, CD142+, CD45+ MPs were determined by flow cytometry, while plasma levels of ICAM-1, VCAM-1, IL-6 by ELISA. In vitro, PMP release and activation of isolated platelets from GGC and PGC were investigated, along with their effect on IL-6 secretion in THP-1 transformed macrophages. Results We found that MPs CD62P+ (PMP) and CD142+ (tissue factor-bearing MP) were significantly higher in PGC T2DM than GGC T2DM and NGT. Among MPs, PMP were also correlated with HbA1c and IL-6. In vitro, we showed that acute thrombin exposure stimulated a significantly higher PMP release in PGC T2DM than GGC T2DM through a more robust activation of PAR-4 receptor than PAR-1 receptor. Treatment with PAR-4 agonist induced an increased release of PMP in PGC with a Ca2+-calpain dependent mechanism since this effect was blunted by calpain inhibitor. Finally, the uptake of PMP derived from PAR-4 treated PGC platelets into THP-1 transformed macrophages promoted a marked increase of IL-6 release compared to PMP derived from GGC through the activation of the NF-kB pathway. Conclusions These results identify PAR-4 as a mediator of platelet activation, microparticle release, and inflammation, in poorly controlled T2DM. Supplementary Information The online version contains supplementary material available at 10.1186/s12933-021-01267-w.
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Affiliation(s)
- Alessandra Giannella
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Giulio Ceolotto
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Claudia Maria Radu
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Arianna Cattelan
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Elisabetta Iori
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Andrea Benetti
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Fabrizio Fabris
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Paolo Simioni
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
| | - Angelo Avogaro
- Metabolic Disease Unit, Department of Medicine-DIMED, Via Giustiniani, 2, 35128, Padova, Italy
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3
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Auclair N, Sané AT, Delvin E, Spahis S, Levy E. Phospholipase D as a Potential Modulator of Metabolic Syndrome: Impact of Functional Foods. Antioxid Redox Signal 2021; 34:252-278. [PMID: 32586106 DOI: 10.1089/ars.2020.8081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Significance: Cardiometabolic disorders (CMD) are composed of a plethora of metabolic dysfunctions such as dyslipidemia, nonalcoholic fatty liver disease, insulin resistance, and hypertension. The development of these disorders is highly linked to inflammation and oxidative stress (OxS), two metabolic states closely related to physiological and pathological conditions. Given the drastically rising CMD prevalence, the discovery of new therapeutic targets/novel nutritional approaches is of utmost importance. Recent Advances: The tremendous progress in methods/technologies and animal modeling has allowed the clarification of phospholipase D (PLD) critical roles in multiple cellular processes, whether directly or indirectly via phosphatidic acid, the lipid product mediating signaling functions. In view of its multiple features and implications in various diseases, PLD has emerged as a drug target. Critical Issues: Although insulin stimulates PLD activity and, in turn, PLD regulates insulin signaling, the impact of the two important PLD isoforms on the metabolic syndrome components remains vague. Therefore, after outlining PLD1/PLD2 characteristics and functions, their role in inflammation, OxS, and CMD has been analyzed and critically reported in the present exhaustive review. The influence of functional foods and nutrients in the regulation of PLD has also been examined. Future Directions: Available evidence supports the implication of PLD in CMD, but only few studies emphasize its mechanisms of action and specific regulation by nutraceutical compounds. Therefore, additional investigations are first needed to clarify the functional role of nutraceutics and, second, to elucidate whether targeting PLDs with food compounds represents an appropriate therapeutic strategy to treat CMD. Antioxid. Redox Signal. 34, 252-278.
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Affiliation(s)
- Nickolas Auclair
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada.,Department of Pharmacology & Physiology and Université de Montréal, Montreal, Quebec, Canada
| | - Alain T Sané
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Edgard Delvin
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Schohraya Spahis
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada.,Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Emile Levy
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada.,Department of Pharmacology & Physiology and Université de Montréal, Montreal, Quebec, Canada.,Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
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4
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Han C, Li S, Yue Q, Li N, Yang H, Zhao Z. Polydopamine-capped AgNPs as a novel matrix overcoming the ion suppression of phosphatidylcholine for MALDI MS comprehensive imaging of glycerophospholipids and sphingolipids in impact-induced injured brain. Analyst 2019; 144:6304-6312. [PMID: 31552925 DOI: 10.1039/c9an01361j] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/24/2024]
Abstract
Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) is a powerful tool for the characterization and localization of analytes without the need for extraction, purification, separation or labeling of samples. However, in tissue sections the most abundant lipids, phosphatidylcholines (PCs), could suppress the signals of other classes of coexisting lipids. In this work, polydopamine (PDA)-capped AgNPs (AgNPs@PDA) were synthesized as a matrix of MALDI MSI to analyze lipids in both positive and negative ion modes. By adjusting the thickness of the PDA layer, the signal of silver cluster ions of AgNPs@PDA was effectively controlled, and the ability of AgNPs@PDA serving as a matrix was optimized. More interestingly, using AgNPs@PDA as a matrix, the sensitivity of PCs was dramatically decreased, and the PC signals were greatly suppressed, while for other lipids (including PE, HexCer, PS, PI, PIP, and ST), they were just the opposite. The reason, we believe, is related to the positively charged surface of AgNPs@PDA, and the polyhydroxy and amino groups of PDA. Benefitting from the suppression of the signals of PCs and the improvement of detection sensitivity of other lipids, 58 glycerophospholipids and 25 sphingolipids in brain tissue sections could be imaged in one run with AgNPs@PDA as a matrix by MALDI MSI, much better than when using traditional organic matrices 2,5-dihydroxybenzoic acid and 9-aminoacridine.
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Affiliation(s)
- Chao Han
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry Chinese Academy of Sciences, Beijing Mass Spectrum Center, Beijing 100190, China.
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5
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Yeung J, Li W, Holinstat M. Platelet Signaling and Disease: Targeted Therapy for Thrombosis and Other Related Diseases. Pharmacol Rev 2018; 70:526-548. [PMID: 29925522 PMCID: PMC6013590 DOI: 10.1124/pr.117.014530] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Platelets are essential for clotting in the blood and maintenance of normal hemostasis. Under pathologic conditions such as atherosclerosis, vascular injury often results in hyperactive platelet activation, resulting in occlusive thrombus formation, myocardial infarction, and stroke. Recent work in the field has elucidated a number of platelet functions unique from that of maintaining hemostasis, including regulation of tumor growth and metastasis, inflammation, infection, and immune response. Traditional therapeutic targets for inhibiting platelet activation have primarily been limited to cyclooxygenase-1, integrin αIIbβ3, and the P2Y12 receptor. Recently identified signaling pathways regulating platelet function have made it possible to develop novel approaches for pharmacological intervention in the blood to limit platelet reactivity. In this review, we cover the newly discovered roles for platelets as well as their role in hemostasis and thrombosis. These new roles for platelets lend importance to the development of new therapies targeted to the platelet. Additionally, we highlight the promising receptor and enzymatic targets that may further decrease platelet activation and help to address the myriad of pathologic conditions now known to involve platelets without significant effects on hemostasis.
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Affiliation(s)
- Jennifer Yeung
- Departments of Pharmacology (J.Y., W.L., M.H.) and Internal Medicine, Division of Cardiovascular Medicine (M.H.), University of Michigan, Ann Arbor, Michigan
| | - Wenjie Li
- Departments of Pharmacology (J.Y., W.L., M.H.) and Internal Medicine, Division of Cardiovascular Medicine (M.H.), University of Michigan, Ann Arbor, Michigan
| | - Michael Holinstat
- Departments of Pharmacology (J.Y., W.L., M.H.) and Internal Medicine, Division of Cardiovascular Medicine (M.H.), University of Michigan, Ann Arbor, Michigan
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6
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Tourdot BE, Stoveken H, Trumbo D, Yeung J, Kanthi Y, Edelstein LC, Bray PF, Tall GG, Holinstat M. Genetic Variant in Human PAR (Protease-Activated Receptor) 4 Enhances Thrombus Formation Resulting in Resistance to Antiplatelet Therapeutics. Arterioscler Thromb Vasc Biol 2018; 38:1632-1643. [PMID: 29748334 PMCID: PMC6023764 DOI: 10.1161/atvbaha.118.311112] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 04/24/2018] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Platelet activation after stimulation of PAR (protease-activated receptor) 4 is heightened in platelets from blacks compared with those from whites. The difference in PAR4 signaling by race is partially explained by a single-nucleotide variant in PAR4 encoding for either an alanine or threonine at amino acid 120 in the second transmembrane domain. The current study sought to determine whether the difference in PAR4 signaling by this PAR4 variant is because of biased Gq signaling and whether the difference in PAR4 activity results in resistance to traditional antiplatelet intervention. APPROACH AND RESULTS Membranes expressing human PAR4-120 variants were reconstituted with either Gq or G13 to determine the kinetics of G protein activation. The kinetics of Gq and G13 activation were both increased in membranes expressing PAR4-Thr120 compared with those expressing PAR4-Ala120. Further, inhibiting PAR4-mediated platelet activation by targeting COX (cyclooxygenase) and P2Y12 receptor was less effective in platelets from subjects expressing PAR4-Thr120 compared with PAR4-Ala120. Additionally, ex vivo thrombus formation in whole blood was evaluated at high shear to determine the relationship between PAR4 variant expression and response to antiplatelet drugs. Ex vivo thrombus formation was enhanced in blood from subjects expressing PAR4-Thr120 in the presence or absence of antiplatelet therapy. CONCLUSIONS Together, these data support that the signaling difference by the PAR4-120 variant results in the enhancement of both Gq and G13 activation and an increase in thrombus formation resulting in a potential resistance to traditional antiplatelet therapies targeting COX-1 and the P2Y12 receptor.
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Affiliation(s)
- Benjamin E Tourdot
- From the Department of Pharmacology (B.E.T., H.S., D.T., J.Y., G.G.T., M.H.)
| | - Hannah Stoveken
- From the Department of Pharmacology (B.E.T., H.S., D.T., J.Y., G.G.T., M.H.)
| | - Derek Trumbo
- From the Department of Pharmacology (B.E.T., H.S., D.T., J.Y., G.G.T., M.H.)
| | - Jennifer Yeung
- From the Department of Pharmacology (B.E.T., H.S., D.T., J.Y., G.G.T., M.H.)
| | - Yogendra Kanthi
- Division of Cardiovascular Medicine, Department of Internal Medicine (Y.K., M.H.), University of Michigan, Ann Arbor.,Ann Arbor Veterans Affairs Health System, MI (Y.K.)
| | - Leonard C Edelstein
- Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, PA (L.C.E.)
| | - Paul F Bray
- Department of Internal Medicine, University of Utah, Salt Lake City (P.F.B.)
| | - Gregory G Tall
- From the Department of Pharmacology (B.E.T., H.S., D.T., J.Y., G.G.T., M.H.)
| | - Michael Holinstat
- From the Department of Pharmacology (B.E.T., H.S., D.T., J.Y., G.G.T., M.H.) .,Division of Cardiovascular Medicine, Department of Internal Medicine (Y.K., M.H.), University of Michigan, Ann Arbor
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7
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Beta-adrenergic antagonists during general anesthesia reduced postoperative pain: a systematic review and a meta-analysis of randomized controlled trials. J Anesth 2015; 29:934-43. [DOI: 10.1007/s00540-015-2041-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 06/21/2015] [Indexed: 12/11/2022]
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8
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Mumaw MM, de la Fuente M, Arachiche A, Wahl JK, Nieman MT. Development and characterization of monoclonal antibodies against Protease Activated Receptor 4 (PAR4). Thromb Res 2015; 135:1165-71. [PMID: 25890453 DOI: 10.1016/j.thromres.2015.03.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/02/2015] [Accepted: 03/30/2015] [Indexed: 01/23/2023]
Abstract
BACKGROUND Protease activated receptor 4 (PAR4) is a G protein coupled receptor (GPCR) which is activated by proteolytic cleavage of its N-terminal exodomain. This generates a tethered ligand that activates the receptor and triggers downstream signaling events. With the current focus in the development of anti-platelet therapies shifted towards PARs, new reagents are needed for expanding the field's knowledge on PAR4. Currently, there are no PAR4 reagents which are able to detect activation of the receptor. METHODS Monoclonal PAR4 antibodies were purified from hybridomas producing antibody that were generated by fusing splenocytes with NS-1 cells. Immunoblotting, immunofluorescence, and flow cytometry were utilized to detect the epitope for each antibody and to evaluate the interaction of the antibodies with cells. RESULTS Here, we report the successful generation of three monoclonal antibodies to the N-terminal extracellular domain of PAR4: 14H6, 5F10, and 2D6. We mapped the epitope on PAR4 of 14H6, 5F10, and 2D6 antibodies to residues (48-53), (41-47), and (73-78), respectively. Two of the antibodies (14H6 and 5F10) interacted close to the thrombin cleavage and were sensitive to α-thrombin cleavage of PAR4. In addition, 5F10 was able to partially inhibit the cleavage of PAR4 expressed in HEK293 cells by α-thrombin. CONCLUSIONS These new antibodies provide a means to monitor endogenous PAR4 expression and activation by proteases on cells.
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Affiliation(s)
- Michele M Mumaw
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Maria de la Fuente
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Amal Arachiche
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - James K Wahl
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, NE, USA
| | - Marvin T Nieman
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
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9
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Cleator JH, Duvernay MT, Holinstat M, Colowick NE, Hudson WJ, Song Y, Harrell FE, Hamm HE. Racial differences in resistance to P2Y12 receptor antagonists in type 2 diabetic subjects. J Pharmacol Exp Ther 2014; 351:33-43. [PMID: 25052834 PMCID: PMC4165026 DOI: 10.1124/jpet.114.215616] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 06/27/2014] [Indexed: 01/21/2023] Open
Abstract
Although resistance to the P2Y12 antagonist clopidogrel is linked to altered drug metabolism, some studies suggest that these pharmacokinetic abnormalities only partially account for drug resistance. To circumvent pharmacokinetic complications and target P2Y12 receptor function we applied the direct P2Y12 antagonist 2-methylthio-AMP (2-methylthioadenosine 5'-monophosphate triethylammonium salt) to purified platelets ex vivo. Platelets were purified from healthy and type 2 diabetes mellitus (T2DM) patients and stimulated with thrombin or the selective protease-activated receptor agonists, protease-activated receptor 1-activating peptide (PAR1-AP), or PAR4-AP. Platelet activation as measured by αIIbβ3 activation, and P-selectin expression was monitored in 141 subjects. Our results demonstrate that, compared with healthy subjects, platelets from diabetic patients are resistant to inhibition by 2-methylthio-AMP, demonstrating P2Y12 pharmacodynamic defects among diabetic patients. Inhibition of thrombin-mediated αIIbβ3 activation by 2-methylthio-AMP was lower in diabetic platelets versus healthy platelets. Subgroup analysis revealed a racial difference in the resistance to 2-methylthio-AMP. We found no resistance in platelets from diabetic African Americans; they were inhibited by 2-methylthio-AMP equally as well as platelets from healthy African Americans. In contrast, platelets from Caucasian patients with diabetes were resistant to P2Y12 antagonism compared with healthy Caucasians. Multivariable analysis demonstrated that other variables, such as obesity, age, or gender, could not account for the differential resistance to 2-methylthio-AMP among races. These results suggest that in addition to altered drug metabolism, P2Y12 receptor function itself is altered in the Caucasian diabetic population. The racial difference in platelet function in T2DM is a novel finding, which may lead to differences in treatment as well as new targets for antiplatelet therapy.
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Affiliation(s)
- John H Cleator
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
| | - Matthew T Duvernay
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
| | - Michael Holinstat
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
| | - Nancy E Colowick
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
| | - Willie J Hudson
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
| | - Yanna Song
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
| | - Frank E Harrell
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
| | - Heidi E Hamm
- Department of Medicine and Division of Cardiovascular Medicine (J.H.C.), Department of Pharmacology (J.H.C., M.T.D., M.H., N.E.C., W.J.H., H.E.H.), and Department of Biostatistics (Y.S., F.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania (M.H.)
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Boknäs N, Faxälv L, Sanchez Centellas D, Wallstedt M, Ramström S, Grenegård M, Lindahl TL. Thrombin-induced platelet activation via PAR4: pivotal role for exosite II. Thromb Haemost 2014; 112:558-65. [PMID: 24990072 DOI: 10.1160/th13-12-1013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 04/20/2014] [Indexed: 01/22/2023]
Abstract
Thrombin-induced platelet activation via PAR1 and PAR4 is an important event in haemostasis. Although the underlying mechanisms responsible for ensuring efficient PAR1 activation by thrombin have been extensively studied, the potential involvement of recognitions sites outside the active site of the protease in thrombin-induced PAR4 activation is largely unknown. In this study, we developed a new assay to assess the importance of exosite I and II for PAR4 activation with α - and γ-thrombin. Surprisingly, we found that exosite II is critical for activation of PAR4. We also show that this dependency on exosite II likely represents a new mechanism, as it is unaffected by blockage of the previously known interaction between thrombin and glycoprotein Ibα.
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Affiliation(s)
| | | | | | | | | | | | - T L Lindahl
- Tomas Lindahl, Department of Clinical and Experimental Medicine, Linköping University, SE-51885 Linköping, Sweden, Tel.: +46 101033227, Fax: +46 101033240, E-mail:
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11
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Sayyah J, Bartakova A, Nogal N, Quilliam LA, Stupack DG, Brown JH. The Ras-related protein, Rap1A, mediates thrombin-stimulated, integrin-dependent glioblastoma cell proliferation and tumor growth. J Biol Chem 2014; 289:17689-98. [PMID: 24790104 DOI: 10.1074/jbc.m113.536227] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Rap1 is a Ras family GTPase with a well documented role in ERK/MAP kinase signaling and integrin activation. Stimulation of the G-protein-coupled receptor PAR-1 with thrombin in human 1321N1 glioblastoma cells led to a robust increase in Rap1 activation. This response was sustained for up to 6 h and mediated through RhoA and phospholipase D (PLD). Thrombin treatment also induced a 5-fold increase in cell adhesion to fibronectin, which was blocked by down-regulating PLD or Rap1A or by treatment with a β1 integrin neutralizing antibody. In addition, thrombin treatment led to increases in phospho-focal adhesion kinase (tyrosine 397), ERK1/2 phosphorylation and cell proliferation, which were significantly inhibited in cells treated with β1 integrin antibody or Rap1A siRNA. To assess the role of Rap1A in tumor formation in vivo, we compared growth of 1321N1 cells stably expressing control, Rap1A or Rap1B shRNA in a mouse xenograft model. Deletion of Rap1A, but not of Rap1B, reduced tumor mass by >70% relative to control. Similar observations were made with U373MG glioblastoma cells in which Rap1A was down-regulated. Collectively, these findings implicate a Rap1A/β1 integrin pathway, activated downstream of G-protein-coupled receptor stimulation and RhoA, in glioblastoma cell proliferation. Moreover, our data demonstrate a critical role for Rap1A in glioblastoma tumor growth in vivo.
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Affiliation(s)
| | - Alena Bartakova
- Pathology, University of California at San Diego, La Jolla, California 92093 and
| | | | - Lawrence A Quilliam
- the Department of Biochemistry and Molecular Biology, Indiana University, Indianapolis, Indiana 46202
| | - Dwayne G Stupack
- Pathology, University of California at San Diego, La Jolla, California 92093 and
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Holinstat M, Colowick NE, Hudson WJ, Blakemore D, Chen Q, Hamm HE, Cleator JH. Dichotomous effects of exposure to bivalirudin in patients undergoing percutaneous coronary intervention on protease-activated receptor-mediated platelet activation. J Thromb Thrombolysis 2013; 35:209-22. [PMID: 23054462 DOI: 10.1007/s11239-012-0812-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Bivalirudin is a direct thrombin inhibitor that is increasingly used in percutaneous coronary intervention (PCI) and has been previously shown to lack inherent platelet activation. Thrombin works through activation of protease activated receptor-1 (PAR1) and PAR4 on human platelets to initiate signaling cascades leading to platelet aggregation. Despite the increasing usage of bivalirudin, the effects on platelet function have not been well defined. Bivalirudin exposure during PCI was therefore assessed for its potential short-term effects on washed platelet function through PAR1 and PAR4. Bivalirudin significantly inhibited low-dose thrombin-mediated platelet aggregation, dense granule secretion, integrin αIIbβ3 activation and Rap1 activation and high dose thrombin-mediated dense granule secretion and Rap1 activation. Exposure to bivalirudin did not alter PAR1 or 4 agonist peptide (PAR1-AP or PAR4-AP) induced aggregation, dense granule secretion, integrin glycoprotein IIbIIIa activation or Rap1 activation. However, exposure to bivalirudin significantly potentiated surface expression of P-selectin following stimulation with high dose thrombin and PAR1-AP, and both low and high dose PAR4-AP. Hence, our data are the first to show that exposure to bivalirudin increased P-selectin expression with certain conditions demonstrating that bivalirudin can increase inherent platelet activity.
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Affiliation(s)
- Michael Holinstat
- Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, PA, USA
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13
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Yeung J, Apopa PL, Vesci J, Stolla M, Rai G, Simeonov A, Jadhav A, Fernandez-Perez P, Maloney DJ, Boutaud O, Holman TR, Holinstat M. 12-lipoxygenase activity plays an important role in PAR4 and GPVI-mediated platelet reactivity. Thromb Haemost 2013; 110:569-81. [PMID: 23784669 DOI: 10.1160/th13-01-0014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 05/30/2013] [Indexed: 12/12/2022]
Abstract
Following initial platelet activation, arachidonic acid is metabolised by cyclooxygenase-1 and 12-lipoxygenase (12-LOX). While the role of 12-LOX in the platelet is not well defined, recent evidence suggests that it may be important for regulation of platelet activity and is agonist-specific in the manner in which it regulates platelet function. Using small molecule inhibitors selective for 12-LOX and 12-LOX-deficient mice, the role of 12-LOX in regulation of human platelet activation and thrombosis was investigated. Pharmacologically inhibiting 12-LOX resulted in attenuation of platelet aggregation, selective inhibition of dense versus alpha granule secretion, and inhibition of platelet adhesion under flow for PAR4 and collagen. Additionally, 12-LOX-deficient mice showed attenuated integrin activity to PAR4-AP and convulxin compared to wild-type mice. Finally, platelet activation by PARs was shown to be differentially dependent on COX-1 and 12-LOX with PAR1 relying on COX-1 oxidation of arachidonic acid while PAR4 being more dependent on 12-LOX for normal platelet function. These studies demonstrate an important role for 12-LOX in regulating platelet activation and thrombosis. Furthermore, the data presented here provide a basis for potentially targeting 12-LOX as a means to attenuate unwanted platelet activation and clot formation.
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Affiliation(s)
- J Yeung
- Michael Holinstat, Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, 1020 Locust Street, Suite 394, Jefferson Alumni Hall, Philadelphia, PA, USA, Tel.: +1 215 955 6121, Fax: +1 215 955 9170, E-mail:
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14
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Duvernay M, Young S, Gailani D, Schoenecker J, Hamm HE, Hamm H. Protease-activated receptor (PAR) 1 and PAR4 differentially regulate factor V expression from human platelets. Mol Pharmacol 2013; 83:781-92. [PMID: 23307185 DOI: 10.1124/mol.112.083477] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
With the recent interest of protease-activated receptors (PAR) 1 and PAR4 as possible targets for the treatment of thrombotic disorders, we compared the efficacy of protease-activated receptor (PAR)1 and PAR4 in the generation of procoagulant phenotypes on platelet membranes. PAR4-activating peptide (AP)-stimulated platelets promoted thrombin generation in plasma up to 5 minutes earlier than PAR1-AP-stimulated platelets. PAR4-AP-mediated factor V (FV) association with the platelet surface was 1.6-fold greater than for PAR1-AP. Moreover, PAR4 stimulation resulted in a 3-fold greater release of microparticles, compared with PAR1 stimulation. More robust FV secretion and microparticle generation with PAR4-AP was attributable to stronger and more sustained phosphorylation of myosin light chain at serine 19 and threonine 18. Inhibition of Rho-kinase reduced PAR4-AP-mediated FV secretion and microparticle generation to PAR1-AP-mediated levels. Thrombin generation assays measuring prothrombinase complex activity demonstrated 1.5-fold higher peak thrombin levels on PAR4-AP-stimulated platelets, compared with PAR1-AP-stimulated platelets. Rho-kinase inhibition reduced PAR4-AP-mediated peak thrombin generation by 25% but had no significant effect on PAR1-AP-mediated thrombin generation. In conclusion, stimulation of PAR4 on platelets leads to faster and more robust thrombin generation, compared with PAR1 stimulation. The greater procoagulant potential is related to more efficient FV release from intracellular stores and microparticle production driven by stronger and more sustained myosin light chain phosphorylation. These data have implications about the role of PAR4 during hemostasis and are clinically relevant in light of recent efforts to develop PAR antagonists to treat thrombotic disorders.
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Affiliation(s)
- Matthew Duvernay
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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15
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Elvers M, Grenegård M, Khoshjabinzadeh H, Münzer P, Borst O, Tian H, Di Paolo G, Lang F, Gawaz M, Lindahl TL, Fälker K. A novel role for phospholipase D as an endogenous negative regulator of platelet sensitivity. Cell Signal 2012; 24:1743-52. [DOI: 10.1016/j.cellsig.2012.04.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 04/25/2012] [Indexed: 02/01/2023]
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16
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Aaltonen N, Lehtonen M, Varonen K, Goterris GA, Laitinen JT. Lipid phosphate phosphatase inhibitors locally amplify lysophosphatidic acid LPA1 receptor signalling in rat brain cryosections without affecting global LPA degradation. BMC Pharmacol 2012; 12:7. [PMID: 22686545 PMCID: PMC3418163 DOI: 10.1186/1471-2210-12-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 06/11/2012] [Indexed: 11/10/2022] Open
Abstract
Background Lysophosphatidic acid (LPA) is a signalling phospholipid with multiple biological functions, mainly mediated through specific G protein-coupled receptors. Aberrant LPA signalling is being increasingly implicated in the pathology of common human diseases, such as arteriosclerosis and cancer. The lifetime of the signalling pool of LPA is controlled by the equilibrium between synthesizing and degradative enzymatic activity. In the current study, we have characterized these enzymatic pathways in rat brain by pharmacologically manipulating the enzymatic machinery required for LPA degradation. Results In rat brain cryosections, the lifetime of bioactive LPA was found to be controlled by Mg2+-independent, N-ethylmaleimide-insensitive phosphatase activity, attributed to lipid phosphate phosphatases (LPPs). Pharmacological inhibition of this LPP activity amplified LPA1 receptor signalling, as revealed using functional autoradiography. Although two LPP inhibitors, sodium orthovanadate and propranolol, locally amplified receptor responses, they did not affect global brain LPA phosphatase activity (also attributed to Mg2+-independent, N-ethylmaleimide-insensitive phosphatases), as confirmed by Pi determination and by LC/MS/MS. Interestingly, the phosphate analog, aluminium fluoride (AlFx-) not only irreversibly inhibited LPP activity thereby potentiating LPA1 receptor responses, but also totally prevented LPA degradation, however this latter effect was not essential in order to observe AlFx--dependent potentiation of receptor signalling. Conclusions We conclude that vanadate- and propranolol-sensitive LPP activity locally guards the signalling pool of LPA whereas the majority of brain LPA phosphatase activity is attributed to LPP-like enzymatic activity which, like LPP activity, is sensitive to AlFx- but resistant to the LPP inhibitors, vanadate and propranolol.
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Affiliation(s)
- Niina Aaltonen
- School of Pharmacy, University of Eastern Finland, P,O, Box 1627, 70211, Kuopio, Finland.
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17
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Nylander M, Osman A, Ramström S, Åklint E, Larsson A, Lindahl TL. The role of thrombin receptors PAR1 and PAR4 for PAI-1 storage, synthesis and secretion by human platelets. Thromb Res 2012; 129:e51-8. [DOI: 10.1016/j.thromres.2011.12.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 11/11/2011] [Accepted: 12/19/2011] [Indexed: 12/16/2022]
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18
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de la Fuente M, Noble DN, Verma S, Nieman MT. Mapping human protease-activated receptor 4 (PAR4) homodimer interface to transmembrane helix 4. J Biol Chem 2012; 287:10414-10423. [PMID: 22318735 DOI: 10.1074/jbc.m112.341438] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thrombin activates platelets by binding and cleaving protease-activated receptors 1 and 4 (PAR1 and PAR4). Because of the importance of PAR4 activation on platelets in humans and mice and emerging roles for PAR4 in other tissues, experiments were done to characterize the interaction between PAR4 homodimers. Bimolecular fluorescence complementation and bioluminescence resonance energy transfer (BRET) were used to examine the PAR4 homodimer interface. In bimolecular fluorescence complementation experiments, PAR4 formed homodimers that were disrupted by unlabeled PAR4 in a concentration-dependent manner, but not by rhodopsin. In BRET experiments, the PAR4 homodimers showed a specific interaction as indicated by a hyperbolic BRET signal in response to increasing PAR4-GFP expression. PAR4 did not interact with rhodopsin in BRET assays. The threshold maximum BRET signal was disrupted in a concentration-dependent manner by unlabeled PAR4. In contrast, rhodopsin was unable to disrupt the BRET signal, indicating that the disruption of the PAR4 homodimer is not due to nonspecific interactions. A panel of rho-PAR4 chimeras and PAR4 point mutants has mapped the dimer interface to hydrophobic residues in transmembrane helix 4. Finally, mutations that disrupted dimer formation had reduced calcium mobilization in response to the PAR4 agonist peptide. These results link the loss of dimer formation to a loss of PAR4 signaling.
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Affiliation(s)
- María de la Fuente
- Division of Hematolgy/Oncology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Daniel N Noble
- Division of Hematolgy/Oncology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Sheetal Verma
- Division of Hematolgy/Oncology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Marvin T Nieman
- Division of Hematolgy/Oncology, Case Western Reserve University, Cleveland, Ohio 44106; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106.
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Schlagenhauf A, Kozma N, Leschnik B, Wagner T, Muntean W. Thrombin receptor levels in platelet concentrates during storage and their impact on platelet functionality. Transfusion 2012; 52:1253-9. [PMID: 22233332 DOI: 10.1111/j.1537-2995.2011.03475.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Quality control of platelet (PLT) concentrates is challenging, due to PLT lesions, which are difficult to detect with routine methods. The search for reliable PLT lesion biomarkers is focused on the role of PLTs in primary hemostasis. PLT transfusions also have a significant impact on secondary hemostasis. In this phase, responsiveness of PLTs to small amounts of thrombin is crucial. PAR1 and PAR4 are protease-activated receptors and are responsible for thrombin reactivity of human PLTs. This study should elucidate if levels of those two receptors are changing in PLT concentrates during storage and if those changes have an impact on PLT aggregation and support of thrombin generation. STUDY DESIGN AND METHODS PLT concentrates from buffy coat preparations were stored in SSP+ solution for 9 days at 22±2°C on a horizontal flatbed agitator, and samples were taken daily for analysis. PAR1 and PAR4 levels were evaluated using Western blot analysis. PLT aggregation was measured using Born aggregometry and specific PAR1 or PAR4 agonists. Thrombin generation was measured using calibrated automated thrombography. RESULTS Levels of both receptors (PAR1 and PAR4) started to decrease after 5 days of storage. PAR1-mediated PLT aggregation remained constant, whereas PAR4-mediated PLT aggregation decreased with storage time. Rate of thrombin generation was accelerated after 5 days of storage. CONCLUSION Decreasing levels of PARs in PLT concentrates after 5 days of storage influenced PAR4-mediated, but not PAR1-mediated, aggregation. Thrombin generation with senescent PLTs was increased, which may be attributed to other mechanisms promoting increased phosphatidylserine exposure.
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Affiliation(s)
- Axel Schlagenhauf
- Department of General Pediatrics and Adolescent Medicine, Medical University of Graz, Graz, Austria
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20
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Han N, Jin K, He K, Cao J, Teng L. Protease-activated receptors in cancer: A systematic review. Oncol Lett 2011; 2:599-608. [PMID: 22848234 DOI: 10.3892/ol.2011.291] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Accepted: 04/06/2011] [Indexed: 12/16/2022] Open
Abstract
The traditional view of the role of proteases in tumor growth, progression and metastasis has significantly changed. Apart from their contribution to cancer progression, it is evident that a subclass of proteases, such as thrombin, serves as signal molecules controlling cell functions through the protease-activated receptors (PARs). Among the four types of PAR (PAR1-4; cloned and named in order of their discovery), PAR1, PAR3 and PAR4 are activated by thrombin, unlike PAR2, which is activated by trypsin-like serine proteases. Thrombin has been proven to be a significant factor in both the behavior of cancer in its involvement in hemostasis and blood coagulation. Thrombin is a key supporter of various cellular effects relevant to tumor growth and metastasis, as well as a potent activator of angiogenesis, which is essential for the growth and development of all solid tumor types. This review presents an overview of the role of PAR-mediated thrombin in angiogenesis and cancer, focusing on the ability of PAR1- and PAR4-mediated thrombin to affect tumorigenesis and angiogenesis.
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Affiliation(s)
- Na Han
- Sir Run Run Shaw Institute of Clinical Medicine, Zhejiang University: Key Laboratory of Biotherapy of Zhejiang Province, Zhejiang University, Hangzhou, Zhejiang 310016
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21
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Adams MN, Ramachandran R, Yau MK, Suen JY, Fairlie DP, Hollenberg MD, Hooper JD. Structure, function and pathophysiology of protease activated receptors. Pharmacol Ther 2011; 130:248-82. [PMID: 21277892 DOI: 10.1016/j.pharmthera.2011.01.003] [Citation(s) in RCA: 267] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 01/03/2011] [Indexed: 12/18/2022]
Abstract
Discovered in the 1990s, protease activated receptors(1) (PARs) are membrane-spanning cell surface proteins that belong to the G protein coupled receptor (GPCR) family. A defining feature of these receptors is their irreversible activation by proteases; mainly serine. Proteolytic agonists remove the PAR extracellular amino terminal pro-domain to expose a new amino terminus, or tethered ligand, that binds intramolecularly to induce intracellular signal transduction via a number of molecular pathways that regulate a variety of cellular responses. By these mechanisms PARs function as cell surface sensors of extracellular and cell surface associated proteases, contributing extensively to regulation of homeostasis, as well as to dysfunctional responses required for progression of a number of diseases. This review examines common and distinguishing structural features of PARs, mechanisms of receptor activation, trafficking and signal termination, and discusses the physiological and pathological roles of these receptors and emerging approaches for modulating PAR-mediated signaling in disease.
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Affiliation(s)
- Mark N Adams
- Mater Medical Research Institute, Aubigny Place, Raymond Terrace, South Brisbane Qld 4101, Australia
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22
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Lenoci L, Duvernay M, Satchell S, DiBenedetto E, Hamm HE. Mathematical model of PAR1-mediated activation of human platelets. MOLECULAR BIOSYSTEMS 2011; 7:1129-37. [DOI: 10.1039/c0mb00250j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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23
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Holinstat M, Boutaud O, Apopa PL, Vesci J, Bala M, Oates JA, Hamm HE. Protease-activated receptor signaling in platelets activates cytosolic phospholipase A2α differently for cyclooxygenase-1 and 12-lipoxygenase catalysis. Arterioscler Thromb Vasc Biol 2010; 31:435-42. [PMID: 21127289 DOI: 10.1161/atvbaha.110.219527] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
OBJECTIVE The rate-limiting step in the biosynthesis of thromboxane A(2) (TxA(2)) and 12-hydroxyeicosatetraenoic acid (12-HETE) by platelets is activation of cytosolic phospholipase A(2α) (cPLA(2α)), which releases arachidonic acid, which is the substrate for cyclooxygenase-1 (COX-1) and 12-lipoxygenase. We evaluated signaling via the human platelet thrombin receptors, protease-activated receptor (PAR) 1 and PAR4, to the activation of cPLA(2α), which provides a substrate for the biosynthesis of TxA(2) and 12-HETE. METHODS AND RESULTS Stimulating washed human platelets resulted in delayed biosynthesis of 12-HETE, which continues after maximal formation of TxA(2) is completed, suggesting that 12-HETE is not formed by the same pool of arachidonic acid that provides a substrate to COX-1. PAR1-induced formation of TxA(2) was inhibited by the phosphatidylinositol kinase inhibitor LY294002, whereas this inhibitor did not block 12-HETE biosynthesis. Both 1-butanol and propranolol also blocked TxA(2) biosynthesis but did not inhibit 12-HETE formation. CONCLUSIONS The concerted evidence indicates that the platelet thrombin receptors signal activation of cPLA(2α) coupled to COX-1 by a pathway different from that signaling activation of the cPLA(2α) coupled to 12-lipoxygenase.
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Affiliation(s)
- Michael Holinstat
- Cardeza Foundation for Hematologic Research, Department of Medicine, Thomas Jefferson University, 1015 Walnut Street, Philadelphia, PA 19107, USA.
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Cirino G, Severino B. Thrombin receptors and their antagonists: an update on the patent literature. Expert Opin Ther Pat 2010; 20:875-84. [PMID: 20450349 DOI: 10.1517/13543776.2010.487864] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
IMPORTANCE OF THE FIELD Thrombin plays a central role in cardiovascular inflammation. Most of the cellular responses to thrombin are mediated by cell surface protease-activated receptors (PARs). Several preclinical studies indicate that PARs are potential targets for treating cardiovascular diseases such as thrombosis, atherosclerosis and restenosis. Among PARs, PAR-1 has emerged as an important therapeutic target. AREAS COVERED IN THIS REVIEW This review covers recent advances in the development of thrombin receptors antagonists. It is focused on the search for PAR-1 antagonists as this is at the moment the most promising and attractive target. However, some early promising studies on PAR-3 and -4 antagonists are also reported. WHAT THE READER WILL GAIN The review has been written in order to give to the reader hints and references that cover, in our opinion, the most interesting and/or promising approaches in this research field. TAKE HOME MESSAGE Research on PAR-1 antagonists has finally led to good clinical candidates such as SCH-530348 (Schering-Plough) and E-5555 (Eisai Co.). Clinical trials clearly demonstrate that development of PAR1 antagonists is not only possible but most likely will lead to development of antiplatelet drugs as well as of drugs useful for the treatment of inflammatory, proliferative and neurodegenerative diseases.
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Affiliation(s)
- Giuseppe Cirino
- University of Naples Federico II, Department of Experimental Pharmacology, Via Domenico Montesano 49, Napoli 80131, Italy.
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25
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Noh JY, Lim KM, Bae ON, Chung SM, Lee SW, Joo KM, Lee SD, Chung JH. Procoagulant and prothrombotic activation of human erythrocytes by phosphatidic acid. Am J Physiol Heart Circ Physiol 2010; 299:H347-55. [DOI: 10.1152/ajpheart.01144.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Increased phosphatidic acid (PA) and phospholipase D (PLD) activity are frequently observed in various disease states including cancers, diabetes, sepsis, and thrombosis. Previously, PA has been regarded as just a precursor for lysophosphatidic acid (LPA) and diacylglycerol (DAG). However, increasing evidence has suggested independent biological activities of PA itself. In the present study, we demonstrated that PA can enhance thrombogenic activities in human erythrocytes through phosphatidylserine (PS) exposure in a Ca2+-dependent manner. In freshly isolated human erythrocytes, treatment of PA or PLD induced PS exposure. PA-induced PS exposure was not attenuated by inhibitors of phospholipase A2or phosphatidate phosphatase, which converts PA to LPA or DAG. An intracellular Ca2+increase and the resultant activation of Ca2+-dependent PKC-α appeared to underlie the PA-induced PS exposure through the activation of scramblase. A marginal decrease in flippase activity was also noted, contributing further to the maintenance of exposed PS on the outer membrane. PA-treated erythrocytes showed strong thrombogenic activities, as demonstrated by increased thrombin generation, endothelial cell adhesion, and erythrocyte aggregation. Importantly, these procoagulant activations by PA were confirmed in a rat in vivo venous thrombosis model, where PA significantly enhanced thrombus formation. In conclusion, these results suggest that PA can induce thrombogenic activities in erythrocytes through PS exposure, which can increase thrombus formation and ultimately contribute to the development of cardiovascular diseases.
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Affiliation(s)
| | | | | | | | - Sang-Wook Lee
- School of Electrical Engineering, Seoul National University, Seoul; and
| | - Kyung-Mi Joo
- Research and Development Center, Amorepacific Company, Gyeonggi-do, Korea
| | - Sin-Doo Lee
- School of Electrical Engineering, Seoul National University, Seoul; and
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Elvers M, Stegner D, Hagedorn I, Kleinschnitz C, Braun A, Kuijpers MEJ, Boesl M, Chen Q, Heemskerk JWM, Stoll G, Frohman MA, Nieswandt B. Impaired alpha(IIb)beta(3) integrin activation and shear-dependent thrombus formation in mice lacking phospholipase D1. Sci Signal 2010; 3:ra1. [PMID: 20051593 DOI: 10.1126/scisignal.2000551] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Platelet aggregation is essential for hemostasis but can also cause myocardial infarction and stroke. A key but poorly understood step in platelet activation is the shift of the principal adhesive receptor, alpha(IIb)beta(3) integrin, from a low- to high-affinity state for its ligands, a process that enables adhesion and aggregation. In response to stimulation of heterotrimeric guanosine triphosphate-binding protein or immunoreceptor tyrosine-based activation motif-coupled receptors, phospholipases cleave membrane phospholipids to generate lipid and soluble second messengers. An essential role in platelet activation has been established for phospholipase C (PLC) but not for PLD and its product phosphatidic acid. Here, we report that platelets from Pld1(-/-) mice displayed impaired alpha(IIb)beta(3) integrin activation in response to major agonists and defective glycoprotein Ib-dependent aggregate formation under high shear conditions. These defects resulted in protection from thrombosis and ischemic brain infarction without affecting tail bleeding times. These results indicate that PLD1 may be a critical regulator of platelet activity in the setting of ischemic cardiovascular and cerebrovascular events.
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Affiliation(s)
- Margitta Elvers
- University Clinic Würzburg and Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080 Würzburg, Germany
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Holinstat M, Preininger AM, Milne SB, Hudson WJ, Brown HA, Hamm HE. Irreversible platelet activation requires protease-activated receptor 1-mediated signaling to phosphatidylinositol phosphates. Mol Pharmacol 2009; 76:301-13. [PMID: 19483102 PMCID: PMC2713123 DOI: 10.1124/mol.109.056622] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 05/29/2009] [Indexed: 01/25/2023] Open
Abstract
Thrombin induces platelet activation through an early, reversible stage of platelet aggregation, which is followed by a later, irreversible stage of platelet aggregation. Without intervention, events leading to pathological platelet activation can result in vessel occlusion, acute coronary syndrome, and stroke. Therefore, a better understanding of events leading to platelet-mediated clot formation may provide insight into new therapeutic targets. Once activated, protease activated receptors (PARs) are essential in regulating events leading to platelet aggregation. We have determined a signaling cascade through PAR1, which involves phosphatidylinositol (PI) kinases, phosphatidylinositol bisphosphate (PIP(2)), and Rap1 activation (independent of P2Y12) in the formation of a stable platelet aggregate. The putative phosphatidylinositol-3 kinase (PI3K) inhibitor LY294002 was found to reduce basal and PAR-stimulated PIP(2) levels by mass spectrometry and to inhibit PAR1-mediated stable platelet aggregation. Rap1 activation in platelets (during time points corresponding to the late, irreversible phase of aggregation) was found to require the PI signaling pathway. Perturbation of PI3K signaling by isoform-selective inhibitors had differential effects on Rap1 activation through PAR1 and PAR4. Hence, it is possible to disrupt lipid signaling pathways involved in stable clot formation without inhibiting early clot formation, offering a new potential target for antiplatelet therapy.
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Affiliation(s)
- Michael Holinstat
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA
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Angiolillo DJ, Bhatt DL, Gurbel PA, Jennings LK. Advances in antiplatelet therapy: agents in clinical development. Am J Cardiol 2009; 103:40A-51A. [PMID: 19166712 DOI: 10.1016/j.amjcard.2008.11.023] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Antiplatelet agents are the cornerstone of treatment for patients with acute coronary syndromes and patients undergoing percutaneous coronary intervention. The current "gold standard" consists of a combination of aspirin and clopidogrel administered orally shortly before invasive procedures and then continued in the form of maintenance doses. Not all patients respond optimally to standard therapy. Resistance to the antiplatelet activity of both drugs when used either singly or in combination has been observed and may lead to treatment failure, including further atherothrombotic events. Potential limitations associated with the combined use of aspirin and clopidogrel have inspired clinical investigation into several promising new antiplatelet agents as potential additions or alternatives to standard therapy. The candidates include prasugrel, which has a mechanism similar to that of clopidogrel but with superior pharmacokinetics; ticagrelor, a nonthienopyridine that binds reversibly to the platelet P2Y(12) receptor; cangrelor, an intravenously administered analogue of ticagrelor; and various thrombin receptor antagonists.
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Nieman MT. Protease-activated receptor 4 uses anionic residues to interact with alpha-thrombin in the absence or presence of protease-activated receptor 1. Biochemistry 2009; 47:13279-86. [PMID: 19053259 DOI: 10.1021/bi801334s] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thrombin activates protease-activated receptor 1 (PAR1) faster than protease-activated receptor 4 (PAR4) due to a hirudin-like sequence in the exodomain of PAR1 that binds thrombin's exosite I. However, recombinant exodomain studies indicate that PAR4 does have extended contacts with alpha-thrombin that influence PAR4's kinetics of cleavage. In this report, the role of an anionic cluster (Asp(57), Asp(59), Glu(62), and Asp(65)) in the exodomain of PAR4 is examined for its influence on cleavage and activation of PAR4 on cells in the absence or presence of PAR1. Alpha-thrombin induces wild-type PAR4 (PAR4-wt) calcium flux with an EC(50) of 110 nM, whereas mutation of the four anionic residues (PAR4-AAAA) increases the EC(50) to 641 nM. In contrast, PAR4-wt and PAR4-AAAA are activated by gamma-thrombin with similar EC(50) values (588 and 449 nM, respectively; p = 0.48), suggesting a role for alpha-thrombin's exosite I in PAR4 activation. Coexpression of PAR1 lowered the EC(50) of cleavage for PAR4-wt from 321 to 26 nM and for PAR4-AAAA from 1.5 microM to 360 nM. Individual point mutations at Asp(57), Asp(59), Glu(62), and Asp(65) show that PAR4-D57A is activated by alpha-thrombin with the same EC(50) as PAR4-wt (140 nM) whereas PAR4-D59A is the same as PAR4-AAAA (699 nM). Glu(62) and Asp(65) contribute to alpha-thrombin recognition, but to a lesser extent. This report shows that PAR4 uses its anionic cluster to interact with alpha-thrombin and that this interaction is important even in the presence of PAR1.
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Affiliation(s)
- Marvin T Nieman
- Division of Hematology/Oncology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-7284, USA.
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Grenegård M, Vretenbrant-Oberg K, Nylander M, Désilets S, Lindström EG, Larsson A, Ramström I, Ramström S, Lindahl TL. The ATP-gated P2X1 receptor plays a pivotal role in activation of aspirin-treated platelets by thrombin and epinephrine. J Biol Chem 2008; 283:18493-504. [PMID: 18480058 DOI: 10.1074/jbc.m800358200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Human platelets express protease-activated receptor 1 (PAR1) and PAR4 but limited data indicate for differences in signal transduction. We studied the involvement of PAR1 and PAR4 in the cross-talk between thrombin and epinephrine. The results show that epinephrine acted via alpha(2A)-adrenergic receptors to provoke aggregation, secretion, and Ca(2+) mobilization in aspirin-treated platelets pre-stimulated with subthreshold concentrations of thrombin. Incubating platelets with antibodies against PAR4 or the PAR4-specific inhibitor pepducin P4pal-i1 abolished the aggregation. Furthermore, platelets pre-exposed to the PAR4-activating peptide AYPGKF, but not to the PAR1-activating peptide SFLLRN, were aggregated by epinephrine, whereas both AYPGKF and SFLLRN synergized with epinephrine in the absence of aspirin. The roles of released ATP and ADP were elucidated by using antagonists of the purinergic receptors P2X(1), P2Y(1), and P2Y(12) (i.e. NF449, MRS2159, MRS2179, and cangrelor). Intriguingly, ATP, but not ADP, was required for the epinephrine/thrombin-induced aggregation. In Western blot analysis, a low concentration of AYPGKF, but not SFLLRN, stimulated phosphorylation of Akt on serine 473. Moreover, the phosphatidyl inositide 3-kinase inhibitor LY294002 antagonized the effect of epinephrine combined with thrombin or AYPGKF. Thus, in aspirin-treated platelets, PAR4, but not PAR1, interacts synergistically with alpha(2A)-adrenergic receptors, and the PI3-kinase/Akt pathway is involved in this cross-talk. Furthermore, in PAR4-pretreated platelets, epinephrine caused dense granule secretion, and subsequent signaling from the ATP-gated P2X(1)-receptor and the alpha(2A)-adrenergic receptor induced aggregation. These results suggest a new mechanism that has ATP as a key element and circumvents the action of aspirin on epinephrine-facilitated PAR4-mediated platelet activation.
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Affiliation(s)
- Magnus Grenegård
- Department of Medicine and Health, Division of Drug Research, Division of Clinical Chemistry, Cardiovascular Inflammation Research Center, Linköping University, Linköping SE-581 85 Sweden.
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Keltai M. Platelet aggregation inhibition in acute coronary syndrome. Facts and expectations. Orv Hetil 2008; 149:483-91. [DOI: 10.1556/oh.2008.28290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A szerző áttekinti az akut coronariaszindróma thrombocytaaggregáció-gátló kezelésének jelenlegi gyakorlatát. Ismerteti a thrombocytaaggregáció-gátlásra használt gyógyszereket, azok adagolását és klinikai hasznosságát. Felhívja a figyelmet arra, hogy a III. fázisú vizsgálatokban alkalmazott gyógyszeradagolás az ismételt vizsgálatok során változhat. Mind az acetilszalicilsav, mind pedig a clopidogrel esetében számolni kell csökkent reaktivitással, amit rezisztenciaként is lehet értelmezni. Mivel ennek jelentősége lehet a klinikai hatékonyság vonatkozásában, ezért is fontos lesz a jövőben a thrombocytaaggregáció-gátlásának mérése, betegágy mellett is használható, gyors, megbízható módszerekkel. A dolgozat végén a szerző áttekinti a kifejlesztés alatt álló újabb thrombocytaaggregáció-gátló szereket.
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Proteinases and signalling: pathophysiological and therapeutic implications via PARs and more. Br J Pharmacol 2007; 153 Suppl 1:S263-82. [PMID: 18059329 DOI: 10.1038/sj.bjp.0707507] [Citation(s) in RCA: 210] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Proteinases like thrombin, trypsin and tissue kallikreins are now known to regulate cell signaling by cleaving and activating a novel family of G-protein-coupled proteinase-activated receptors (PARs 1-4) via exposure of a tethered receptor-triggering ligand. On their own, short synthetic PAR-selective PAR-activating peptides (PAR-APs) mimicking the tethered ligand sequences can activate PARs 1, 2 and 4 and cause physiological responses both in vitro and in vivo. Using the PAR-APs as sentinel probes in vivo, it has been found that PAR activation can affect the vascular, renal, respiratory, gastrointestinal, musculoskeletal and nervous systems (both central and peripheral nervous system) and can promote cancer metastasis and invasion. In general, responses triggered by PARs 1, 2 and 4 are in keeping with an innate immune inflammatory response, ranging from vasodilatation to intestinal inflammation, increased cytokine production and increased or decreased nociception. Further, PARs have been implicated in a number of disease states, including cancer and inflammation of the cardiovascular, respiratory, musculoskeletal, gastrointestinal and nervous systems. In addition to activating PARs, proteinases can cause hormone-like effects by other signalling mechanisms, like growth factor receptor activation, that may be as important as the activation of PARs. We, therefore, propose that the PARs themselves, their activating serine proteinases and their associated signalling pathways can be considered as attractive targets for therapeutic drug development. Thus, proteinases in general must now be considered as 'hormone-like' messengers that can signal either via PARs or other mechanisms.
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Bilodeau ML, Hamm HE. Regulation of protease-activated receptor (PAR) 1 and PAR4 signaling in human platelets by compartmentalized cyclic nucleotide actions. J Pharmacol Exp Ther 2007; 322:778-88. [PMID: 17525299 DOI: 10.1124/jpet.107.121830] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Thrombin potently regulates human platelets by the G protein-coupled receptors protease-activated receptor (PAR) 1 and PAR4. Platelet activation by thrombin and other agonists is broadly inhibited by prostacyclin and nitric oxide acting through adenylyl and guanylyl cyclases to elevate cAMP and cGMP levels, respectively. Using forskolin and YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole] to selectively activate the adenylyl and guanylyl cyclases, respectively, and the membrane-permeable analogs N(6),2'-O-dibutyryladenosine-3'-5'-cAMP (dibutyryl-cAMP) and 8-(4-parachlorophenylthoi)-cGMP (8-pCPT-cGMP), we sought to identify key antiplatelet steps for cyclic nucleotide actions in blocking platelet activation by PAR1 versus PAR4. Platelet aggregation by PAR1 or PAR4 was inhibited with similar EC(50) of 1.2 to 2.1 microM forskolin, 31 to 33 microM YC-1, 57 to 150 microM dibutyryl-cAMP, and 220 to 410 microM 8-pCPT-cGMP. There was a marked left shift in the inhibitory potencies of forskolin and YC-1 for alpha-granule release and glycoprotein IIbIIIa/integrin alphaIIbbeta3 activation (i.e., EC(50) of 1-60 and 40-1300 nM, respectively) that was not observed for dibutyryl-cAMP and 8-pCPT-cGMP (i.e., EC(50) of 200-600 and 40-140 microM, respectively). This inhibition was essentially instantaneous, and measurements of cyclic nucleotide levels and kinase activities support a model of compartmentation involving the cyclic nucleotide effectors and regulators and the key molecular targets for this platelet inhibition. The different sensitivities of PAR1 and PAR4 to inhibition of calcium mobilization and dense granule release identify key antiplatelet steps for cyclic nucleotide actions and are consistent with the signaling models for these receptors. Specifically, PAR4 inhibition depends on the regulation of both calcium mobilization and dense granule release, and PAR1 inhibition depends predominantly on the regulation of dense granule release.
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Affiliation(s)
- Matthew L Bilodeau
- Department of Pharmacology, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, 442 Robinson Research Building, Nashville, TN 37232-6600, USA
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Voss B, McLaughlin JN, Holinstat M, Zent R, Hamm HE. PAR1, but not PAR4, activates human platelets through a Gi/o/phosphoinositide-3 kinase signaling axis. Mol Pharmacol 2007; 71:1399-406. [PMID: 17303701 DOI: 10.1124/mol.106.033365] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Thrombin-mediated activation of platelets is critical for hemostasis, but the signaling pathways responsible for this process are not completely understood. In addition, signaling within this cascade can also lead to thrombosis. In this study, we have defined a new signaling pathway for the thrombin receptor protease activated receptor-1 (PAR1) in human platelets. We show that PAR1 couples to G(i/o) in human platelets and activates phosphoinositide-3 kinase (PI3K). PI3K activation regulates platelet integrin alphaIIbbeta3 activation and platelet aggregation and potentiates the PAR1-mediated increase in intraplatelet calcium concentration. PI3K inhibitors eliminated these effects downstream of PAR1, but they had no effect on PAR4 signaling. This study has identified an important role for the direct activation of G(i/o) by PAR1 in human platelets. Given the efficacy of clopidogrel, which blocks the G(i/o)-coupled P2Y purinoceptor 12, as an antiplatelet/antithrombotic drug, our data suggest that specifically blocking only PAR1-mediated G(i/o) signaling could also be an effective therapeutic approach with the possibility of less unwanted bleeding.
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Affiliation(s)
- Bryan Voss
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA
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